3 second character input lag for large filesbrowsing

Running a large-ish file locally (about 30 MB), NP++ will freeze and not let me do anything for about 3 seconds after inputting a character. Sometimes it even stops responding and takes longer. deleting characters is instantaneous, though. On regular notepad with the exact same file open, the issue does not exist at all. I have a brand-new high-end laptop, so hardware is not the issue.